smear

Smear is a term used in everyday language and in many professional disciplines. As a verb, it means to spread or daub a substance over a surface, often producing a smeared, indistinct mark. As a noun, a smear is the resulting mark or layer, such as a smear of lipstick on a glass, a smudge on a window, or a thin layer prepared for examination under a microscope. The sense of "smear" thus encompasses both the action and its visible trace.

Etymology: The word comes from Old English smearian or smeoran, meaning to rub or spread; related forms appear in several Germanic languages.

In medicine and biology, a smear often refers to a preparation made by spreading a thin film of cells or microorganisms on a slide for microscopic analysis. Blood smear, where a drop of blood is spread on a slide, is used to examine blood cells. The Pap smear, or Papanicolaou test, is a screening method for cervical cancer that examines cells collected from the cervix. Microbiological smears and Gram smears are common in labs. In pathology, a smear may be stained to reveal cellular details.

In dentistry and material science, a smear layer can form on dentin during instrumentation, consisting of debris and organic matter. It can affect bonding of restorative materials. The broader sense of smeared residues appears in cleaning, manufacturing, and forensics when a surface bears unintended marks or trace evidence.

In politics and media, a smear refers to a campaign to damage someone’s reputation through misleading or false statements; a smear campaign aims to cast doubt on a person’s character or integrity.